1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for transmitting/receiving control information in a broadband wireless communication system using Half Frequency Division Duplex (H-FDD).
2. Description of the Related Art
In general, a wireless communication system is designed to enable data transmission/reception between two parties. To support such data transmission/reception, the wireless communication system separates a transmission/reception channel on the basis of frequency or time and uses the separated transmission/reception channel for each party. Frequency Division Duplex (FDD) represents a scheme of dividing a transmission/reception channel on a frequency axis and performing communication. Time Division Duplex (TDD) represents a scheme of dividing a transmission/reception channel on a time axis and performing communication. The FDD scheme requires filtering a receive signal to cancel interference that may occur due to the introduction of a transmit signal into a reception unit. Also, because a transmission unit and a reception unit must be separately provided, a realization cost increases.
To address these concerns, a Half FDD (H-FDD) scheme realizable by a single transmitting/receiving unit that implements the merits of the FDD scheme has been proposed. Like the FDD scheme, the H-FDD scheme distinguishes a transmission channel and a reception channel at a frequency axis, but carries out transmission and reception during a different time. Thus, considering only one transmit end and receive end, the H-FDD scheme wastes a half resource compared to the FDD scheme. However, in a conventional wireless communication system in which a Base Station (BS) and a plurality of Mobile Stations (MSs) perform communication, a resource waste is prevented by grouping the MSs into two groups and applying a different transmission pattern to each group as illustrated in FIG. 1. That is, as illustrated in FIG. 1, while first-group H-FDD MSs receive DownLink (DL) signals 111 through DL bands, second-group H-FDD MSs transmit UpLink (UL) signals 121 through UL bands. And, while the first-group H-FDD MSs transmit UL signals 115 through UL bands, the second-group H-FDD MSs receive DL signals 125 through DL bands. At this time, because there is only one transmission/reception unit, each MS requires Transmit/receive Transition Gap (TTG) intervals 113 and 127 for conversion from a reception mode to a transmission mode and Receive/transmit Transition Gap (RTG) intervals 117 and 123 for conversion from the transmission mode to the reception mode.
As described above, by applying the H-FDD scheme, an MS may include only one transmission/reception unit. However, as illustrated in FIG. 1, there is no interval in which MSs that belong to different groups simultaneously receive DL signals. In this case, there is a problem in transmitting system information required to be commonly transmitted by a BS to all the MSs. For example, in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system, MSs cannot perform communication until acquiring control information such as a Cyclic Prefix (CP) length, a bandwidth, resource block information, antenna related information, etc. If there is no interval in which MSs that belong to different groups simultaneously receive DL signals as in FIG. 1, a BS must repeatedly transmit the control information separately for each group, i.e., the BS must repeat transmission a number of times equal to the number of groups. However, the control information is an overhead and, with an increase of the number of times of transmission of the control information, a resource available for data transmission decreases. Thus, there is a need for an apparatus and method for transmitting control information using less overhead in a wireless communication system using H-FDD.